While these results provide important information regarding the relationship between PTSD and alcohol dependence, there were limitations that should be considered. The present study was small in comparison to other GWAS. Larger sample sizes are desirable for genetic association studies due to the small effects of loci typically detected in GWAS. Further, these analyses do not consider the temporality of PTSD and alcohol dependence diagnoses. Future studies should examine the age or timing of onset for each disorder to unpack the causal relationships between PTSD and alcohol dependence beyond shared genetic risk. In addition, limited information was available on trauma exposure type (e.g., assaultive, nonassaultive) for the entire sample. Initial phases in COGA only assessed whether an individual experienced a traumatic event without asking the individual specific questions regarding their traumatic exposure. Therefore, influence of trauma type on these associations was not investigated. Given the known sex differences in exposure rates and influences of different trauma types on risk of PTSD and alcohol dependence, future studies should examine whether polygenic risk of PTSD differs depending on trauma type.
